This one is quick and short. I have been asked few time, how can we check what value was specified to OSDBA, OSOPER and OSASM,especially during upgrades (to know what was it set to which initial installation)
# The DBA_GROUP is the OS group which is to be granted OSDBA privileges.
# The OPER_GROUP is the OS group which is to be granted OSOPER privileges.
# The OSASM_GROUP is the OS group which is to be granted OSASM privileges.
The below is from GRID_HOME :-
[grid@testdb1 dbs]$ grep “define SS_” $ORACLE_HOME/rdbms/lib/config.c
#define SS_DBA_GRP “asmdba”
#define SS_OPER_GRP “”
#define SS_ASM_GRP “asmadmin”
Even installation logfiles can be checked.